1. Field of the Invention
The present invention relates to an air conditioner, and more particularly to an air conditioner which automatically controls operation based on supply voltage or supply frequency.
2. Description of the Background Art
An air conditioner which detects operating current, controls a compressor and a fan motor, and controls switch timing of a defrosting operation has been developed recently. Examples of such an air conditioner are those disclosed in Japanese Patent Laying-Open No. 6-101896 and Japanese Patent Laying-Open No. 5-44980.
Referring to FIG. 1, the air conditioner disclosed in Japanese Patent Laying-Open No. 6-101896 includes: a current detector 20; a rectifying/smoothing unit 2 connected to an output of current detector 20; an inverter 23 connected to an output of rectifying/smoothing unit 2 and a microcomputer 21 which is described later; a compressor motor 22 connected to an output of inverter 23; a fan drive unit 26 connected to the output of current detector 20 and microcomputer 21; a fan motor 24 connected to an output of fan drive unit 26; an outside air temperature detector 25; and microcomputer 21 controlling respective units such as fan drive unit 26 and inverter 23 based on an output from current detector 20 and an output from outside air temperature detector 25.
Current detector 20 detects a total amount of input current fed by the power supply. Rectifying/smoothing unit 2 rectifies and smoothes alternating current diverging from the input current. Inverter 23 obtains alternating current in a prescribed frequency range from direct current output from rectifying/smoothing unit 2, based on an inverter control signal output from microcomputer 21. Compressor motor 22 receives the alternating current output from inverter 23, and compresses refrigerant in a refrigerating cycle. Fan drive unit 26 controls a rotating speed of fan motor 24 based on a fan drive control signal output from microcomputer 21. Fan motor 24 promotes heat dissipation from a heat exchanger, electronic parts and the like. Microcomputer 21 controls inverter 23 and fan drive unit 26 based on the total amount of the input current detected by current detector 20 and based on an outside air temperature.
Referring to FIG. 2, the air conditioner disclosed in the Japanese Patent Laying-Open No. 6-101896 operates as follows. The steps S1, S2 and S5 in the figure relate to control of each unit of the air conditioner based on the outside air temperature output from outside temperature detector 25. The steps S3 and S4 relate to control of each unit of the air conditioner based on the total amount of the input current output from current detector 20.
Microcomputer 21 determines whether the outside air temperature detected by outside air temperature detector 25 has a prescribed set value or less (step S1). If the outside air temperature is equal to or less than the prescribed set value (YES in step S1), microcomputer 21 transmits a fan drive control signal to fan drive unit 26 to allow fan motor 24 to perform a normal operation. Fan drive unit 26 receiving the fan drive control signal enables fan motor 24 to carry out the normal operation (step S5). The step S1 is thereafter carried out again.
If the outside air temperature is more than the prescribed set value (NO in step S1), microcomputer 21 transmits a fan drive control signal to fan drive unit 26 such that drive current of fan motor 24 attains the maximum value. Fan drive unit 26 receiving the fan drive control signal makes the drive current of fan motor 24 maximum (step S2). A process of step S3 is thereafter performed.
In step S3, microcomputer 21 determines whether the input current detected by current detector 20 is equal to or less than a prescribed maximum value (step S3). If the input current has the prescribed maximum value or less (YES in step S3), the process of step S1 is carried out with the current state maintained. If the input current exceeds the prescribed maximum value (NO in step S3), microcomputer 21 transmits an inverter control signal to inverter 23 to decrease frequency of inverter 23 (step S4). Accordingly, an output from compressor motor 22 is reduced.
Referring to FIG. 3, the air conditioner disclosed in the Japanese Patent Laying-Open No. 5-44980 includes: an alternating current power supply 7; a sensor 27; a rectifier 31; an inverter 29; a compressor 30; an inverter output current detection sensor 28; a power consumption computing unit 32; and an air conditioning controller 33.
Sensor 27 detects power consumption of an input portion of the air conditioner. Inverter output current detection sensor 28 detects a value of output current of inverter 29 supplied from inverter 29 to compressor 30. Power consumption computing unit 32 receives the power consumption of the input portion of the air conditioner, the value of output current of inverter 29, and a voltage value of current supplied to inverter 29 obtained by smoothing an output from rectifier 31, and calculates power consumption of the air conditioner. Air conditioning controller 33 receives the power consumption calculated by power consumption computing unit 32, and determines operating frequency of compressor 30 to make a capacity controllable. Air conditioning controller 33 drives inverter 29 with this frequency, and controls the air conditioner such that the highest limit of power consumption of the air conditioner has a prescribed set value or less.
The conventional air conditioners as described above are controlled to prevent current value and power consumption of the air conditioner from increasing to a fixed value or more. On the other hand, control for securing reliability of the an conditioner, or control of an operation switch timing is possible. However, for example, in Europe where supply voltage is different according to countries, if the same air conditioner is used, current varies depending on supply voltage. Therefore, it is difficult to appropriately control an air conditioner using the same detected current value. In such a country as Japan where supply frequency is different according to regions, an air conditioner, including a motor or the like having its current value which is dramatically changed according to frequencies, can not be stably and reliably controlled using the same current value.